Examples of commonly used wick materials are cellulose, either in the form of cardboard (pressed pulp) or fibres; porous plastic, in particular those made by POREX™ (Porex Technologies, Fairburn, US) or Micropore Plastics (Royal Woods Parkway Tucker, Ga., US), and others; graphite; and ceramic.
There is a trend in the industry to use natural materials, as consumers will often prefer these. Some plant stem materials, in particular bamboo and rattan, are known to function as wicks.
The transfer or evaporation rate of a liquid through a particular wick material depends to a considerable extent on the nature of the liquid, the difference between aqueous and non-aqueous liquids being particularly marked. The degree of absorbency of all of these wick materials in a given liquid is also variable. Thus, different wick materials are selected for different applications, depending on the nature of the liquid desired to be transferred.
Many common wick materials, such as porous plastic and rattan, have a limited porosity and transfer or evaporation rate, partially due to blocking or slow transfer of at least part of fragrance ingredients (for example due to fractionation and/or blocking).
Fractionation over time will change the character and/or intensity of the fragrance and will slow evaporation. Particularly problematic in terms of evaporation properties including the occurrence of fractionation are fluids comprising actives that, for example, occur in crystalline form in nature, have a high molecular weight, or low vapour pressure.
Similarly, there is a need for emanators that provide for efficient transfer and evaporation of a liquid received by contact to a wick.
Therefore, there remains a need for a transfer element (wick, emanator) material that has a good absorbency and can efficiently transfer both aqueous and non-aqueous liquids comprising the abovementioned actives at a good evaporation rate without significant fractionation.